Objective
The purpose of this study was to titrate the nerve block effect of phenol with different concentrations of phenol solution by electrophysiological and mechanical measurements.

Method
Right tibial nerves of twenty three adult rabbits were blocked by phenol solution with different concentrations (3%, 5%). Nerve conduction study for compound muscle action potential (CMAP), tension by electrical stimulation, and stiffness (slope) of stretch reflex of the triceps surae were performed after nerve block (4 weeks, 8 weeks, 16 weeks). The ratios of each values of right limb to those of left limb were used to evaluate the nerve block effect.

Results
The ratios of CMAP amplitude, tension, and slope of 3% group were 0.36, 0.55, and 0.56 at 4 weeks and those of 5% group were 0.21, 0.25, and 0.58. There were statistically significant differences of the CMAP amplitude and tension ratios, however there was no statistically significant difference of the slope ratio between two groups at 4 weeks. The ratios of CMAP amplitude, tension, and slope of 5% phenol group were increased with time.

Conclusion
Nerve block effects by 5% phenol solution were greater than 3%. These data suggest that nerve block effect can be titrated with concentration of phenol solution.